Not Applicable.
1. The Field of the Invention
The present invention relates generally to ligament and tendon graft attachment devices, and more particularly, but not necessarily entirely, to a ligament fixation system having adjustable tightening qualities.
2. Description of Related Art
This invention relates to tibial fixation for anterior or posterior cruciate ligament reconstruction of the knee. Current practice involves the use of screws, staples, spiked washers, or suture buttons to secure a ligament substituted to the tibia. The ability to secure the ligament substituted within the bone (endosteal) is known in the prior art.
Apparatus and methods for attaching ligaments to bone have been developed and are preexisting in the prior art. Typically, these devices either attach a ligament graft to the exterior of a bone, or within a drill hole bored through the endosteal portion of the bone. The strength of the graft attachment in such systems is usually dependent on the cancellous bone density of the bone.
There are several other ligament fixation devices known in the prior art, such as that disclosed in U.S. Pat. No. 4,870,957 (the xe2x80x9c""957 patentxe2x80x9d), which is incorporated by reference herein in its entirety. The device disclosed in the ""957 patent features an eyelet attached to a stud. A ligament graft is placed into the eyelet by looping the graft and passing the looped graft through a channel in the stud to the eyelet. The stud is then passed into a drill hole bored into the bone. A threaded footing is placed in the drill hole, disposed on threads tapped into the walls defining the drill hole. The stud is seated within a portion of the threaded footing in a type of rotational interference fit, and the threaded footing is then turned on the tapped threads until a desired ligament tension is reached. This system thus requires the drill hole in the bone to be threaded, an additional surgical procedure that introduces the potential of the bone threads stripping or being misaligned. It further requires the stud to be placed into the drill hole from the same direction in which the ligament graft enters, increasing the complexity of the surgery and the number of items that must pass through the joint across which the ligament passes. An additional limiting factor is that the device can only be used with grafts that are formed into loops. The device shown in the ""957 patent thus would not be suitable for use with bone-tendon-bone (BTB) implants, including the recent anterior cruciate ligament (ACL) reconstruction technique that involves flipping one end of a patellar tendon autograft (PTA), details of which are described in Barber, A. F., Flipped Patellar Tendon Autograft Anterior Cruciate Ligament Reconstruction, Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol. 16. No. 5, pp 483-490, (July-August, 2000), which is hereby incorporated by reference herein in its entirety.
Implanting a BTB ligament graft has been traditionally accomplished by inserting the graft into a drill hole bored into a bone, and by inserting a screw next to the bone plug of the graft to compress the bone plug against the wall of the drill hole. Examples of this technique are found in Barber (cited above), and in U.S. Pat. No. 5,282,802, which is hereby incorporated by reference herein in its entirety. Since the graft is held in place by frictional engagement between the bone plug and the wall of the drill hole, the strength of the attachment is proportional to the density of the bone. Additionally, the screw must be placed against the cancellous side of the bone plug, rather than the cortical side, to reduce the chances of graft pullout. Such factors limit the positions in which the bone plug may be rotated. Such fixation factors also do not allow for simple adjustment of the graft tension.
Other prior art devices operate either by holding a graft within a bone channel by compressing a pretensioned graft between its own components, such as that disclosed in U.S. Pat. No. 4,708,132 to Silvestrini, which is incorporated by reference in its entirety, or by attaching the graft to connectors located on the exterior surface of the bone, such as that disclosed in U.S. Pat. No. 4,778,468 to Hunt et al., or U.S. Pat. No. 4,772,286 to Goble et al., each of which is incorporated by reference herein in its entirety. By placing a connector on the exterior surface of the bone, such devices leave the connector exposed to soft tissues, which can lead to sensitivity, or potential pain if the area is bumped sufficiently to cause the soft tissue to strike the connector or to cause other complications. The prior art is thus characterized by several disadvantages that are addressed by the present invention. The present invention minimizes, and in some aspects eliminates, the above-mentioned failures, and other problems, by utilizing the methods and structural features described herein.
It is therefore an object of the present invention to provide a ligament graft or tendon graft attachment system that is simple in design and manufacture.
It is another object of the present invention to provide such a ligament graft attachment system that can be used with any graft substitute.
It is an additional object of the present invention to provide such a ligament graft system in which the graft fixation strength is not dependent on the cancellous bone density of the bone.
It is a further object of the present invention to provide such a ligament graft attachment system that enables the tension of the ligament graft to be adjusted.
It is an additional object of the present invention to provide such a system that can be completely recessed into the bone.
It is another object of the present invention, in accordance with one aspect thereof, to provide a ligament graft attachment system that may be inserted and attached through a hole drilled in the bone, without fully inserting a component into the joint.
It is yet another object of the invention, in accordance with one aspect thereof, to provide a ligament graft attachment system that uses a stepwise interference fit to adjust the ligament graft tension.
The above objects and others not specifically recited are realized in a specific illustrative embodiment of an endosteal tibial ligament fixation system with adjustable tensioning. A grasping hook located on a shaft is used to draw a ligament graft into a contoured drill hole formed in a bone. A series of slanted ridges on the shaft can pass in only one direction through a securing push nut residing in the contoured drill hole, resulting in a interference fit that secures the attachment system, while allowing the tension of the ligament graft to be adjusted.
One advantage of the invention device is that it accommodates all currently know graft substitutes, bone patellar tendon bone, Achilles tendon bone, central quad tendon, and hamstring tendons. This device also anticipates the eventual development of an artificial ligament which would have a closed loop at the tibial end. Thus this device would be suitable for every ACL/PCL surgeon.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the invention without undue experimentation. The objects and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.